Colin Gleadell has the surprises from the Old Master sales:

• The surprise of the Bonhams sale was a view of the River Adda ascribed to the studio of the 18th-century Italian view painter Vanvitelli. As the Vanvitelli expert had not given the painting a full attribution, it was estimated at a modest £20,000. But at least two bidders were willing to pit their wits against the expert, and it sold for £385,250.

• In 1978, an unidentified artist bought a portrait of a boy attributed vaguely to the “circle of ” Frans Hals at Christie’s for £5,500. Having been heavily painted over in the past, the small panel was cleaned in the 1980s but yielded no clues as to its precise authorship. It was not until earlier this year that the Dutch restorer Martin Bijl was given the painting and, after cleaning by him, the panel was recognised by experts as being solely the work of Frans Hals. That done, it sold for £241,250.

• A swifter judgment was forthcoming on a portrait of Sally Siddons, the daughter of the actress Sarah Siddons, by Sir Thomas Lawrence. In January this year, it was sold by Sotheby’s in New York, as a joint work by Lawrence and his studio assistants, for $62,500. But after it had been cleaned, Christie’s reinstated the work as fully by Lawrence, and sold it for £313,250 or $489,000

Old master sales: when art restorers clean up (Telegraph)